(i) Technical Field
The present invention relates to an image forming apparatus that obtains a color toner image by overlaying toner images of plural colors on each other.
(ii) Related Art
There is known an image forming apparatus that obtains a color toner image by overlaying toner images of plural colors on each other. In many cases, such an image forming apparatus adjusts toner-image formation positions of toner-image forming units that form toner images of respective colors in order to overlay the toner images with high accuracy. When shifts of the current toner-image formation positions are detected for the adjustment, a method using a registration mark including a set of toner patterns formed by the toner-image forming units of the respective colors is frequently employed. With this method, the shifts of the toner-image formation positions are obtained by detecting the position of the registration mark formed on a transferred member such as an intermediate transfer belt and calculating the shifts based on the detection result.